The Society of Automotive Engineers (SAE) publishes many new, revised, and reaffirmed standards each year in three categories, including Ground Vehicle Standards (J-Reports). Information on these standards is available on the World Wide Web at http://www.sae.org.
Two of these SAE standards are relevant to this invention. SAE J1318 pertains to gaseous discharge warning lamps for authorized emergency, maintenance, and service vehicles. The standard defines a 360.degree. warning lamp as a lamp that projects a light in a horizontal 360.degree. arc. The lamp appears to project a regularly repeating pattern of flashes to an observer positioned at a fixed location. The function of a 360.degree. warning lamp is to inform other highway users to stop, to yield right-of-way, or to indicate the existence of a hazardous situation.
The J1318 standard defines three different classes of warning lamps, (Classes 1, 2 and 3), and specifies different photometric requirements for each class. Reprinted herebelow are the photometric requirements, for a Class 3 warning lamp as recited in Tables 3 and 7, respectively, of J1318. (All candela-second measurements are to be made by sensors placed at least 18 meters from the source.)